Ancient Arabic writings used to reconstruct climate.

Scientists believe ancient Arabic writings could reveal climate change patterns from over a thousand years ago. A study in the journal, Weather, looks at writings of scholars, historians and diarists from the period referred to as the Islamic Golden Age (816-1009AD) to assess the climate of the period.

This is not the first attempt at reconstructing climates from written records; there have been other studies which have assessed the climate during the ‘Little Ice Age’, where the River Thames froze and temperatures were estimated at around one degree colder than at present. Others have looked further back at medieval records of conditions in Europe, but this new study assesses Iraqi writings from over a thousand years ago.

But scientists are usually very wary of using this sort of ‘qualitative’ data to assess past climates. When there are no instrumental records, proxies are used to reconstruct the climate record. This might include tree ring data, which can be extended back thousands of years, ice core data, which can stretch hundreds of thousands, and corals, which can help reconstruct tropical climates.

The disadvantage of these types of proxies is the uncertainty involved or ‘confidence’ that the proxy responded to a stimulus a thousand years ago in the same way it does now. There are so many variables which make a proxy record that it is not always easy to know whether a tree ring has been responding to temperature in exactly the same way for such a long time.

One potential solution is to use documented accounts of the climate. In some instances, a diary entry stating that a river was frozen, or that the rain caused flooding, can give a unique insight to the climate that other proxies cannot offer.

Lead author on the report, Dr. Fernando Dominguez-Castro says, "Climate information recovered from these ancient sources mainly refers to extreme events which impacted wider society such as droughts and floods," said lead author Dr Fernando Domínguez-Castro. "However, they also document conditions which were rarely experienced in ancient Baghdad such as hailstorms, the freezing of rivers or even cases of snow."

Using the surviving works of al-Tabari, Ibn al-Athir and al-Suyuti, the researchers found an increase in cold weather in the first half of the 10th century and reports of several snowfall events. In modern Baghdad, the only snowfall in living memory was seen in 2008. This has led the researchers to surmise that the current climate is warmer than previously.

Moving forward, it is hoped that this study will encourage others to look to written accounts to answer questions on ancient weather.

"Ancient Arabic documentary sources are a very useful tool for finding eye witness descriptions which support the theories made by climate models," says Domínguez-Castro. "The ability to reconstruct past climates provides us with useful historical context for understanding our own climate. We hope this potential will encourage Arabic historians and climatologists to work together to increase the climate data rescued from across the Islamic world."